Positioning devices of this type are often used in servo track writers (STW), in which the tracks for magnetizable hard disks are formatted or written. For this purpose, a positioning device in the STW swivels a shaft, to which a swivel arm is attached. At its end, a write head is provided, which is ultimately moved by the swivel motion of the shaft and is positioned in a highly precise manner so that as many tracks as possible per unit surface area of the hard disk may be configured. The number of tracks set up per unit surface area or unit diameter (tracks per inch) is a measure for the storage capacity of hard disks. For this reason, efforts are permanently undertaken to achieve a track allocation that is as tight as possible. For a hard disk manufacturer to be able to configure hard disks with a dense track allocation in an economical manner, it must be possible to position the swivel arm of the STW in an exact manner within a very short time (seek and settle time).
The publication “Servo Track Writing Technology” (Fujitsu Sci. Tech. J., 37, 2, pages 220 to 226) of December 2001 describes positioning devices, in which the position of the swivel arm is scanned by a separate scanning unit. In this instance, there is considerable expenditure involved in positioning the scanning unit relative to the swivel arm.
In U.S. Pat. No. 5,796,542, an air bearing is used in a servo track writer to increase the running smoothness and to reduce the seek and settle time. Air bearings of this kind may require a highly precise and costly manufacture and a permanent compressed air supply.
Conventional positioning devices may have the disadvantage that they either have a comparatively costly design and/or may be disadvantageous in terms of precision and seek and settle time.